Decompression valve problems Ariel NG

[keith.mettam]

If John's method of detaching the operating lever with the assembly in situ doesn't work for you Will then take the whole unit out and, using soft jaws in a vice, grip the body in the vice with the flats of the body overlapping and touching the top of each vice jaw. Having previously loosened the lever's nut and backed it off (as explained by John) give the end of the spindle a whack downwards with a hammer. If you have a copper hammer so much the better as less chance of damaging the nut or thread on the spindle. Providing you have slackened the nut off enough, a good whack should break the lever's taper fit and you can carry on and dismantle the unit. You have nothing to lose as you have a new decompressor on order !
All the best,
Keith.

[william.forsth]

Hi John, thanks for the picture, it makes perfect sense. This is obvious how it ought to be, mine is in a slightly upward and forward position, and I cant get it to change, wont come apart. I just ordered a new one from draganfly, so I can set it correctly. Hopfully this is the end of my problems, the engine loosing power and dying quite quickly. I think it is due to the fact that it decompressesdue to the little lift arm presses don on it. It is some markings on the metal inside on the valve that shows it has been hitting each other for a while sothe distance between them been less than zero.

Thanks again all, Ill be back soon, either with this or other stuff I am afraid.

W

[william.forsth]

Keith _ I will try that, as you say, I have nothing to loose, and this is war....ish of some sort

[nevhunter]

You might get away with a thick rocker cover gasket. Nev

[john.nash]

One other thing about these lifters, I have found.
When things expand with heat, then a lifter that is literally just touching the top of the valve will nw hold it just open (which may explain your problem)
This also explains why the lifter on a cold engine migt not work but is fine on a hot engine.

[nevhunter]

The little round pin actually touches on a protrusion from the front rocker arm. If the push rod was too short the rocker would have this point too high and you could not adjust it properly. Also the cam follower face could have been dressed down or worn causing the same problem as a short pushrod would. Often the exhaust cam does wear on an Ariel ohv because hot oil runs down the pushrod tube and it can be too thin to oil well. Nev

[william.forsth]

Thanks for the info Nevhunter, that might be it, I replaced the decompresion valve, but I still have the problem, and I have this metalic clonking sound I cant place, it is easy to start, runs for a while, and then dies.... any thoughts?

[john.nash]

Might be, a I mentioned earlier, that when your engine get's hot a lifter that is just engaging will now hold the valve off it's seat.
Also the noise might be related to the valve hitting the lifter on the way up.
It's alright for these old geezers with decades of experience but it took me a while to get the hang of adjusting the lifter just so

Nev is a 100% right (but don't tell him I said so) in that the wrong length pushrod or gasket will let push the valve adujuster "shelf/lip" on the rocker arm to sit up too high. Been there; done that

Easy to eliminate. Just back off the lifter completely OR take it out all together and then start and run the engine.

Apart from that, engines that die can can only be lack of spark, lack of fuel or lack of compression.
The compression one is easy .. when it's stopped, is there compression on the kick start still ?

[brenton.roy]

Hi Will,
John's advice makes sense - not bad for a young bloke.
The most likely thing if it starts and runs Ok is that it is running out of fuel - rust in the fuel line? - float needle not working, that kind of thing.
The first check would be to remove the fuel line and see what comes out. Sludge can sometimes build up around the tap inside the fuel tank and slow fuel flow.
You could blow through the line back into the tank.
Can you restart the bike if it has been running and the motor is warm? If so, this makes ignition trouble less likely, and helps rule out problems caused by things expanding when hot.
How long does it run for?
Does it die slowly, or just cut out?
Where (roughly) is the knock? - bottom, middle or top? Sometimes you can hear noises by listening through a long screwdriver. It's better to put the handle end to your ear...
Brenton

[pete.collings]

A problem I recently encountered with someone else's VH was linked to the valve lifter. The bike started and ran, but after a short while stopped and would not restart. On closer inspection, a different exhaust rocker box had been fitted, and the decompressor had a thick washer behind it. On removing the decompressor assembly, and looking at the length of the peg on the end of the central spindle, it became apparent that it was only just touching the ledge of the rocker arm, and that the movement of the rocker when running had caused the peg to slip under the ledge and then hinder the exhaust valve closing. Removing the thick washer and replacing it with the original crushable copper/asbestos washer, and also swopping the decompressor central spindle for one with a longer peg cured the problem. Subsequent checks on removing the dome screw on the end of the rocker spindle to replace the gasket also showed the spindle was too far across in the rocker box, which would have moved the rocker arm across and reduced the contact area of the peg on the rocker arm ledge. By slackening off the dome nut securing the oil feed, it was possible to move the spindle across until it was just below the end of the rocker box itself, which in turn should move the rocker arm across as well.
I have also seen exhaust rocker arms with damage to the ledge (a bit missing), probably caused by a poorly adjusted lifter being hit by the decompressor peg when the engine was running. Always adjust the decompressor so that the valve lifts only at the last bit of travel of the lifter lever, with plenty of slack in the cable.